Pain and the brain

Pain and the brain

Trevor Petrie - Chief Medical Officer
4 minute read

Everyone experiences pain differently. This is something that is, most likely, readily apparent to anyone reading this article. The question is, "Why?".

I can have 3 people come into my clinic with the same injury or diagnosis, with ostensibly the same level of injury according to imaging and other objective measures, but with wildly different reports of pain.

As someone experiencing pain, especially chronic pain, being on the other side of this phenomenon can be extremely frustrating and invalidating. But there are a whole host of factors that can influence our perception of pain.

There are no "pain nerves"

The first thing to remember is that there are no "pain nerves". We have what are called "nociceptors" which are nerves that respond to noxious stimuli that may cause harm to our bodies.

These are incredibly helpful nerves, since without them we may not know that we’re resting our hand on a hot stove or are in danger of developing a pressure ulcer on our tailbone because we haven’t shifted our weight in our dangerously un-ergonomic home office chair in a very long time.

But the signals from these nerves aren’t directly the cause of pain. "Pain" is how our brains interpret these signals.

There is no "pain center"

The second thing to remember is that there isn’t a "pain center" in our brains, per se. Signals from our peripheral nerves are transmitted up our spinal cords, through our midbrains and then, generally, to the appropriate spot on our sensory cortex.

Obviously, this is a gross oversimplification of this process, but I’m somewhat limited by the need to keep this blog post short as well as my own limited understanding of all the minutiae involved in neural transmission. So if you happen to be a neuroscientist reading this post, please forgive me.

Why we feel pain differently

Now, why do we all have different perceptions of pain when we get signals from our nociceptors? Well, one reason is that everyone’s nerves have different levels of stimulation required to make them fire. This is called a nerve’s "threshold". A nerve’s threshold can change over time depending on a variety of factors including the health of the nerve and the amount of regular input it receives.

Between the nerve ending and the brain, the signal from the nerve has to travel to the spinal cord and then up to the midbrain and then finally to the sensory cortex. Along this route, different peoples bodies will release different neural regulators such as γ-Aminobutyric Acid (GABA) and opioid peptides that change the intensity of the signal as it travels along the course of the neural pathways.

Finally, it’s been shown that our preconceptions or expectations of pain can change the experience of pain once it reaches our brains. Emotional well-being and mindfulness can help alter our perception of the signals relayed to our brains by our peripheral nociceptors. Endorphins released during exercise and activities that bring us happiness, also act to blunt our pain experience.

For two more sources of in-depth, yet understandable explanation of pain, especially chronic pain, I highly recommend checking out the work of Moseley and Butler in their book Explain Pain, as well as Greg Lehman’s online Pain Workbook. Both of these resources go into further detail as to how our environment and our mental and physical health all contribute to our perception of pain. As these authors explain, pain is a multifaceted experience and our understanding of the causes of pain are continuously evolving.

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